Summary Kaposi's sarcoma-associated herpesvirus (KSHV) is a human herpesvirus that causes primary effusion B cell lymphoma (PEL), particularly in patients with acquired immunodeficiency syndrome (AIDS). PEL tumorigenesis is largely driven by the interference of viral oncogenes with normal cell biology. Accordingly, KSHV-positive PEL derived cell lines require continued viral infection for their survival and proliferation in culture. The specific cellular genes and pathways required for KSHV to cause lymphomas, however, are not fully known. In the last two years, efficient methods for gene editing in human cell lines have become available and have been adapted for genome-scale knock-out screens. We have conducted genome-wide CRISPR/Cas9- mediated knockout screens to comprehensively identify cellular genes and pathways necessary for KSHV-induced PEL cell survival and proliferation. In Aim 1, we propose to identify and validate a core set of genes required for the survival of PEL cell lines. In Aim 2, we propose to focus on the biology of a set of functionally related genes that were identified as essential for PEL cell survival and proliferation in our preliminary CRISPR/Cas9 screen. The proposed work for Aim 2 includes the in depth validation of the requirement of these genes for PEL cell survival and proliferation, and experiments to investigate how these genes collaborate in a gene expression cascade. Together, these aims are expected to result in a comprehensive overview of key players in KSHV- mediated B cell transformation and may identify new drug targets.